MIT’s inflatable antennae could boost small satellite communications

Mylar-based attennae could inflate once launched, withstand micro-meteor threat, MIT says.

Researchers at the Massachusetts's Institute of technology say they have developed an inflatable antenna for small satellites known as cubesats that can fold into a compact space and inflate when in orbit.

The inflatable antenna lets a CubeSat transmit data back to Earth at a distance that can be covered by a satellite outfitted with an inflatable antenna is seven times farther than that of existing CubeSat communications, the MIT researchers said in a release.

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"With this antenna you could transmit from the moon, and even farther than that," says Alessandra Babuscia, who led the research as a postdoc at MIT. "This antenna is one of the cheapest and most economical solutions to the problem of communications."

The group also tested each antenna's electromagnetic properties - an indication of how well an antenna can transmit data. In radiation simulations of both the conical and cylindrical designs, the researchers observed that the cylindrical antenna performed slightly better, transmitting data 10 times faster, and seven times farther, than existing CubeSat antennae, the researchers said.

The MIT researcher noted that large, far-ranging radio dishes are impossible to store in a CubeSat's tight quarters. Instead, the satellites are equipped with smaller, less powerful antennae, restricting them to orbits below those of most geosynchronous satellites.

One of the main issues facing the researchers was getting the antennae to inflate with a minimum of effort.  Previous experiments in space have successfully tested such designs, though mostly for large satellites: To inflate these bulkier antennae, engineers install a system of pressure valves to fill them with air once in space - heavy, cumbersome equipment that would not fit within a CubeSat's limited real estate, the researchers said.

For the inflatable antennae which is made from Mylar, the MIT engineers used what's known as sublimating powder -- in this case benzoic acid  -- a chemical compound that transforms from a solid powder to a gas when exposed to low pressure.

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"It's almost like magic.  Once you are in space, the difference in pressure triggers a chemical reaction that makes the powder sublimate from the solid state to the gas state, and that inflates the antenna." Babuscia said.

The team also noted that Mylar-based antennae could be vulnerable to micro meteor strikes but that testing has shown the device can withstand the holes that hazard might create. "Sublimating powder will only create as much gas as needed to fully inflate an antenna, leaving residual powder to sublimate later, to compensate for any later leaks or punctures," Babuscia said.

The researchers found that with the right sublimating powder, the lifetime of a CubeSat's inflatable antenna may be a few years, even if it is riddled with small holes.

The MIT researchers said they were refining the antenna's design at NASA's Jet Propulsion Laboratory.

Kar-Ming Cheung, an engineer specializing in space communications operations JPL, said in a statement MIT's design addresses today's main limitations in CubeSat communications: size, weight and power.

"A directional antenna has been out of the question for CubeSats," says Cheung, who was not involved in the research. "An inflatable antenna would enable orders of magnitude improvement in data return. This idea is very promising."

Depending on whose designing them, CubeSats are tiny satellites with typical dimensions of about 10×10×10 centimeters, weighing a little less than 3lbs, and typically using commercial off-the-shelf electronics components.

There are larger cubesats of course.  For example, asteroid mining company Deep Space Industries said that in 2015 it intends to send out a squadron of 55lb cubesats called Fireflies that will explore near-Earth space for two to six months looking for target asteroids.

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